Conventionally, tunneling magnetoresistive (TMR) sensors are provided with a free layer and a side shield positioned on at least one end of the free layer in a cross-track direction. The side shield has a structure in which a bias field is applied to the free layer. The free layer forms a single magnetic domain as a result of the bias field and noise is suppressed. If the free layer does not form a single magnetic domain and magnetic domains are present, noise, such as Barkhausen noise, is produced.
In a conventional TMR head structure according to the prior art, as shown in FIG. 1, the close-packed plane 106 of the side shield 104 has a small anisotropic field, Hk, perpendicular to the air bearing surface (ABS) 108. The close packed plane 106 is only shown on one side of the side shield 104 to avoid confusion, but the entire side shield 104 is characterized by this close packed plane 106 orientation. This perpendicular orientation acts to reduce the bias field being applied to the free layer of the sensor 102. As a result, noise is generated which reduces the signal-to-noise ratio (SNR) of the TMR head 100. This is undesirable.